Co-axial catheter and method of implanting same

ABSTRACT

A co-axial catheter assembly ( 100 ) including a first lumen ( 110 ) having a first distal end ( 114 ) and a first proximal end ( 112 ), and a second lumen ( 120 ) having a second distal end ( 124 ) and a second proximal end ( 122 ). The second lumen ( 120 ) extends co-axially with the first lumen ( 110 ), wherein the second lumen is at least partially disposed within the first lumen and the second distal end extends distally of the first distal end. The second distal end ( 124 ) includes a distal tip ( 130 ) and a bulbous projection ( 240 ) disposed between the distal tip and the first distal end. A method of inserting the catheter is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a Divisional application of U.S. patentapplication Ser. No. 10/961,706 filed Oct. 8, 2004, which claims thebenefit of U.S. Provisional Patent Application Ser. No. 60/509,626,filed on 8 Oct. 2003.

BACKGROUND OF THE INVENTION

Catheters for the introduction or removal of fluids may be located invarious venous locations and cavities throughout the body forintroduction or removal of these fluids. Such catheterization may beperformed by using a single catheter having multiple lumens. A typicalexample of a multiple lumen catheter is a dual lumen catheter in whichone lumen introduces fluid and the other lumen removes fluid. An exampleof such multiple lumen catheter is the SPLIT-CATH® catheter.

Generally, to insert any catheter into a blood vessel, the vessel isidentified by aspiration with a long hollow needle in accordance withthe well known Seldinger technique. When blood enters a syringe attachedto the needle, indicating that the vessel has been found, a thin guidewire is then introduced, typically through a syringe needle or otherintroducer device into the interior of the vessel. The introducer deviceis then removed, leaving the guide wire within the vessel. The guidewire projects beyond the surface of the skin. At this point, severaloptions are available to a physician for catheter placement. Thesimplest is to pass a catheter into the vessel directly over the guidewire. The guide wire is then removed, leaving the catheter in positionwithin the vessel. However, this technique is only possible in caseswhere the catheter is of a relatively small diameter, made of a stiffmaterial, and not significantly larger than the guide wire, for example,for insertion of small diameter dual lumen catheters. If the catheter tobe inserted is significantly larger than the guide wire, a dilatordevice is passed over the guide wire to enlarge the hole. The catheteris then passed over the guide wire, and the guide wire and dilator arethen removed.

Several different designs of dual lumen catheters are known. One designincorporates side-by-side lumens in which one lumen (the arterial lumen)draws fluid from the body and the other lumen (the venous lumen)delivers fluid to the body. The venous lumen is typically longer thanthe arterial lumen to reduce recirculation of the fluid. One drawback ofthe side-by-side catheter is the fact that, during use, the suctioneffect of the arterial lumen occasionally draws the side wall of thevessel into which the catheter is inserted against the lumen,effectively reducing the ability of fluid to flow into the catheter.

An alternative design is a coaxial design, such as is disclosed in U.S.Pat. No. 5,480,380. In such a catheter design, the arterial lumen isperipheral to the venous lumen, which extends along the longitudinalaxis of the catheter. Like the side-by-side catheter, the venous lumenin the coaxial catheter is typically longer than the arterial lumen toreduce recirculation. One problem with this design is that the inletopenings on the arterial lumen are on the sides of the lumen. The mostproximal opening is typically the only opening that receives heparin orother anti-clotting agent in between treatments, allowing the remainingopenings to clot. Also, the suction effect of the arterial lumen maydraw the lumen against the side wall of the vessel, reducing theavailable surface area of the openings, thereby restricting flow intothe lumen.

It would be beneficial to provide a coaxial catheter that reduces thepotential for a suction effect of the arterial lumen against a vesselwall, and maximizes the amount of fluid that may be taken in by thelumen during catheter operation.

BRIEF SUMMARY OF THE PRESENT INVENTION

Briefly, the present invention provides a co-axial catheter comprising afirst lumen extending along an axis and a second lumen extending alongthe axis. The first lumen has an open first distal end and a firstproximal end and the second lumen is disposed generally within the firstlumen. The second lumen also includes a second distal end extendingdistally of the first distal end. At least one spacer is disposedbetween the first lumen and the second lumen at the distal end of thefirst lumen.

Further, the present invention also provides a co-axial cathetercomprising a first lumen having a first distal end, a first proximalend, and a longitudinal axis extending therethrough and a second lumenhaving a second distal end, a second proximal end, and extendingco-axially with the first lumen. The second lumen is at least partiallydisposed within the first lumen. The second distal end extends distallyof the first distal end, wherein the second distal end includes a distaltip and a bulbous projection disposed between the distal tip and thefirst distal end.

Also, the present invention provides a method of inserting a cathetercomprising providing a catheter having a first lumen having a firstdistal end, a first proximal end, and a longitudinal axis extendingtherethrough and a second lumen having a second distal end, a secondproximal end, and extending co-axially with the first lumen. The secondlumen is at least partially disposed within the first lumen and thesecond distal end extends distally of the first distal end. The seconddistal end includes a distal tip and a bulbous projection disposedbetween the distal tip and the first distal end. The method furthercomprises inserting the distal tip into a blood vessel; and oscillatingthe distal tip in a generally circular motion while advancing the distaltip into the vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitutepart of this specification, illustrate the presently preferredembodiments of the invention, and, together with the general descriptiongiven above and the detailed description given below, serve to explainthe features of the invention. In the drawings:

FIG. 1 is a perspective view of a catheter assembly according to a firstembodiment of the present invention.

FIG. 2 is an enlarged side profile view, in section, of a distal end ofthe catheter assembly of FIG. 1.

FIG. 3 is an enlarged perspective view, in section, of a hub portion ofthe catheter assembly of FIG. 1.

FIG. 3A is an enlarged side profile view, in section, of the hub portionof FIG. 3, with a first embodiment of a spacer inserted therein.

FIG. 3B is an enlarged side profile view, in section, of an alternateembodiment of a hub portion, with a second embodiment of a spacerinserted therein.

FIG. 3C is a sectional view of the hub portion and spacer taken alonglines 3C-3C of FIG. 3B.

FIG. 3D is an enlarged side profile exploded cross-sectional view of ahub portion of another alternate embodiment of a hub portion, with athird embodiment of a spacer for being inserted therein.

FIG. 3E is an enlarged perspective view of the third embodiment of thespacer shown in FIG. 3D.

FIG. 4 is a sectional view showing the manufacturing of the distal endof the catheter assembly of FIG. 1.

FIG. 5 is an enlarged perspective view, in partial section, showing themanufacturing of the hub portion of the catheter assembly of FIG. 1.

FIG. 5A is an enlarged sectional view showing insertion of mandrels usedto manufacture the hub portion shown in FIGS. 3B and 3C.

FIG. 6 is a perspective view, partially broken away, of a catheterassembly according to a second embodiment of the present invention.

FIG. 6A is an enlarged perspective view of the distal end of the outerlumen of the catheter assembly shown in FIG. 6.

FIG. 7 is an enlarged side profile view, in section, of a distal end ofthe catheter assembly of FIG. 6.

FIG. 8 is a sectional view showing the manufacturing of the distal endof the catheter assembly of FIG. 6.

FIG. 8A is a perspective view of a mandrel used to fabricate thecatheter assembly of FIG. 6.

FIG. 9 is a perspective view of an optional distal end of the catheterassembly shown in FIGS. 6 and 7.

FIG. 10 is a side elevation view, in section, of a bulbous tip moldbeing applied over the distal end of the catheter assembly of FIG. 6.

FIG. 11 is a partially broken away view of the catheter assembly of FIG.9 subcutaneously tunneled in a body.

FIG. 12 is partially broken away view of the catheter assembly of FIG.11, having been inserted into an area to be catheterized.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings, like numerals indicate like elements throughout. Asused herein, the term “distal” is defined to mean a direction closer tothe insertion end of the catheter and the term “proximal” is defined tomean a direction closer to the end of the catheter that remains exteriorof the patient after insertion.

A perspective view of a co-axial catheter assembly 100 according to afirst embodiment of the present invention is shown in FIG. 1, with apartial sectional view shown in FIG. 2. The catheter assembly 100includes a proximal end 102 and a distal end 104. The catheter assembly100 also includes an outer lumen 110 and an inner lumen 120, with boththe outer lumen 110 and the inner lumen 120 being co-axial alonglongitudinal axis “A”. The outer lumen 110 includes a proximal end 112,a distal end 114, and a generally cylindrical body 116 extending betweenthe proximal end 112 and the distal end 114. Preferably, the body 116has an outer diameter of approximately 0.50 cm (0.19″) and an innerdiameter of approximately 0.38 cm (0.15″).

The body 116 includes a plurality of side openings 118 helically spacedalong the body 116 proximate to the distal end 114 of the outer lumen110. Preferably, approximately five side openings 118 are present,although more or less than five side openings 118 may be used.Preferably, also, each side opening 118 has a diameter of approximately0.17 cm (0.07″). Preferably, the outer lumen 110 is constructed fromTECOFLEX® having a hardness of 85 A on the Shore Durometer scale.

The inner lumen 120 includes a proximal end 122, a distal end 124, and agenerally cylindrical body 126 extending between the proximal end 122and the distal end 124. Preferably, the body 126 has an outer diameterof approximately 0.28 cm (0.11″) and an inner diameter of approximately0.23 cm (0.09″). Since the outer diameter of the inner lumen body 126 issmaller than the inner diameter of the outer lumen body 116, a firstpassageway 119 (see FIG. 2) is formed between the outer lumen body 116and the inner lumen body 126. Also, since the outer lumen body 116 andthe inner lumen body 126 are co-axial along the longitudinal axis “A”,the first passageway 119 has a generally annularly shaped cross section.The first passageway 119 fluidly communicates with each of the openings118 and serves to draw fluid, such as blood, from the body of thepatient into which the catheter assembly 100 has been inserted.

The distal end 124 of the inner lumen 120 extends distally of the distalend 114 of the outer lumen 110. The body 126 includes a plurality ofside openings 128 helically spaced along the body 126 proximate to thedistal end 124 of the inner lumen 120. Preferably, approximately fiveside openings 128 are present, although more or less than five sideopenings 128 may be used. Preferably, also, each side opening 128 has adiameter of approximately 0.10 cm (0.04″). A second passageway 129 isformed in the inner lumen 120, and serves to return the fluid that wasdrawn from the patient's body by the first passageway 119 and/or addadditional fluids, such as medicaments, into the patient.

A distal tip 130, located at the distal most end of the distal end 124,includes a conical taper and an opening 132 located along thelongitudinal axis “A”. Preferably, the opening 132 has a diameter ofapproximately 0.10 cm (0.04″). Preferably, the inner lumen 120 isconstructed from TECOFLEX® having a hardness of 60 D on the ShoreDurometer scale.

While the outer lumen and inner lumen 110, 120, respectively, arepreferably constructed from TECOFLEX®, those skilled in the art willrecognize that the lumens 110, 120 may alternatively be constructed fromanother biocompatible plastic or elastomer, more preferably from abiocompatible elastomer. Suitable biocompatible plastics includematerials such as, for example, polyethylene, homopolymers andcopolymers of vinyl acetate such as ethylene vinyl acetate copolymer,polyvinylchlorides, homopolymers and copolymers of acrylates such aspolymethylmethacrylate, polyethylmethacrylate, polymethacrylate,ethylene glycol dimethacrylate, ethylene dimethacrylate andhydroxymethyl methacrylate, polyurethanes, polyvinylpyrrolidone,2-pyrrolidone, polyacrylonitrile butadiene, polycarbonates, polyamides,fluoropolymers such as homopolymers and copolymers ofpolytetrafluoroethylene and polyvinyl fluoride, polystyrenes,homopolymers and copolymers of styrene acrylonitrile, cellulose acetate,homopolymers and copolymers of acrylonitrile butadiene styrene,polymethylpentene, polysulfones, polyesters, polyimides,polyisobutylene, polymethylstyrene and other similar compounds known tothose skilled in the art. It should be understood that these possiblebiocompatible polymers are included above for exemplary purposes andshould not be construed as limiting. If a biocompatible polymericmaterial is used to form the lumens 110, 120, it is most preferred thatthe polymeric material includes a polyurethane or a polyolefin polymericmaterial having a preferably soft durometer, as specified below.

Suitable, preferred, biocompatible elastomers for use in forming thelumens 110, 120 include biocompatible elastomers such as medical gradesilicone rubbers, polyvinyl chloride elastomers, polyolefinhomopolymeric and copolymeric elastomers, urethane-based elastomers, andnatural rubber or other synthetic rubbers. Preferably, the lumens 110,120 are made of the elastomeric material such that they are flexible,durable, soft, and easily conformable to the shape of the area to becatheterized and minimize risk of harm to vessel walls. If the lumens110, 120 are used for hemodialysis applications, they are preferablyformed of a soft silicone elastomer which has a hardness of at leastabout 60-D on a Shore durometer scale. Such an elastomer is availablefrom Dow Corning, and can include 20% barium sulfate in the elastomer toprovide radiopacity. While it is preferred to have a higher Shoredurometer hardness if a biocompatible elastomer is used, particularlyfor hemodialysis, it is also possible to make a device from an elastomerhaving a lower Shore durometer hardness without departing from thespirit of the invention. It will be understood, based on thisdisclosure, that the lumens 110, 120 may also be radiopaque depending ontheir intended use.

A spacer 140 is disposed between the outer lumen 110 and the inner lumen120 at the distal end 114 of the outer lumen 110. The spacer 140 closesoff the distal end 114 of the outer lumen 110 and forms a taperedportion 142 extending distally from distal end 114 that fixedly connectsthe distal end 114 of the outer lumen 110 to the distal end 124 of theinner lumen 120. An enlarged sectional view of the distal end 124 of thecatheter assembly 100, showing the spacer 140, is shown in FIG. 2.

Referring now to FIG. 3, the proximal end 112 of the outer lumen 110 andthe proximal end 122 of the inner lumen 120 both terminate in a hub 150.Inside the hub 150, the inner lumen 120 exits the outer lumen 110.Optionally, referring to FIG. 3A, a spacer 151 may be disposed betweenthe proximal end 112 of the of the outer lumen 110 and the proximal end122 of the inner lumen 120 to maintain the coaxial relationship of theinner lumen 120 with respect to the outer lumen 110. Preferably, thespacer 151 has a concave upper face that is curved to match the outercurvature of the inner lumen 120 and a convex lower face that is curvedto match the inner curvature of the outer lumen 110.

Alternatively, a hub 250 is shown in FIG. 3B. The hub 250 is similar tothe hub 150 as described above, but the hub 250 includes a hub cap 256at a proximal end 250 a of the hub 250. In order to maintain spacing ofthe inner lumen 120 and the outer lumen 110, a spacer 251 may beinserted into the hub 250 proximally of the junction of venous andarterial hub passageways 252, 253, respectively. The spacer 251preferably includes a beveled distal end 251 a to block the venouspassageway 253 and to direct fluid flow through the arterial passageway252 between the outer lumen 110 and a first extension tube 160. Thearterial passageway 252 tapers to a narrowed diameter at the proximalend 112 of the outer lumen 110 in order to provide enhanced fluid flowthrough the arterial passageway 252 and to provide a positive stop forthe proximal end 112 of the outer lumen 110. As shown in thecross-sectional view of FIG. 3C, the spacer 251 also includes a key 251b that serves to properly align the spacer 251 within a keyway 253 a inthe venous passageway 253 and to properly align the tapered distal end251 a to properly block the venous passageway 253.

Referring back to FIG. 3B, a proximal end 251 c of the spacer 251includes a stepped member 254 that engages the proximal end 250 a of thehub 250. The proximal end 251 c of the spacer 251 also includes aplurality of through openings 255 located proximally of the steppedmember 254. The through openings 255 allow a wicking adhesive, such asLOCTITE®, to be inserted therein to wick along the boundary between theinner lumen 120 and the spacer 251 to secure the spacer 251 to the innerlumen 120.

The hub cap 256 is disposed over the proximal end 250 a of the hub 250to sandwich the stepped member 254 between the proximal end 250 a of thehub 250 and the hub cap 256. The hub cap 256 provides a connection pointfor a second extension tube 162 to enable fluid communication betweenthe second extension tube 162 and the inner lumen 120.

Another embodiment of a hub 350 that may be used with the catheterassembly 100 is shown in FIGS. 3D and 3E. The hub 350 includes a spacer351 that is disposed within the proximal end 350 a of the hub 350. Thespacer 351 is inserted over the proximal end 122 of the inner lumen 120and into the hub 350 in the direction of the arrow E. The spacer 351includes a plurality of through openings 355 located at the proximal endof the spacer 351. The through openings 355 allow a wicking adhesive,such as LOCTITE®, to be inserted therein to wick along the boundarybetween the inner lumen 120 and the spacer 351 to secure the spacer 351to the inner lumen 120. The spacer 351 also include a plurality oflongitudinal channels 357 that extend along the exterior of the spacer351. The channels 357 allow an adhesive, such as LOCTITE®, to beinserted therein to wick along the boundary between the spacer 351 andthe hub 350 to secure the spacer 351 within the hub 350. Although notshown, a transverse channel may be formed along the exterior of thespacer 351 at distal ends of the channels 357 to fluidly connect thechannels 357 to each other, and to allow the adhesive to provide acircumferential seal between the hub 350 and the spacer 351.

The spacer 351 preferably includes a tapered distal end 351 a to blockthe venous passageway 353 and to direct fluid flow through the arterialpassageway 352 between the outer lumen 110 and the first extension tube160. The arterial passageway 352 tapers to a narrowed diameter at theproximal end 112 of the outer lumen 110 in order to provide enhancedfluid flow through the arterial passageway 352 and to provide a positivestop for the proximal end 112 of the outer lumen 110. The spacer 351also includes a key 351 b that serves to properly align the spacer 351within a keyway 353 a in the venous passageway 353 and to properly alignthe tapered distal end 351 a to properly block the venous passageway353.

A hub cap 356 is overmolded proximate of the proximal end 350 a of thehub 350 to fixedly retain the spacer 351 within the hub 350 and the hubcap 356. During overmold, some hub cap material may flow into the keyway353 a proximal of the key 350 a to retain the spacer 351 within the hub350. The hub cap 356 provides a connection point for a second extensiontube 162 to enable fluid communication between the second extension tube162 and the inner lumen 120.

While the remainder of the description of the hub portion of thecatheter assembly 100 recites the hub 150 without the spacer 151, thoseskilled in the art will recognize that the same description applies toeither the hub 150 with the spacer 151 or to either the hub 250 or thehub 350. Referring back to FIG. 3, the proximal end 112 of the outerlumen 110 fluidly communicates with a first extension tube 160 withinthe hub 150. A distal end 161 of the first extension tube 160 isdisposed within and secured by the hub 150. The proximal end 122 of theinner lumen 120 fluidly communicates with a second extension tube 162within the hub 150. A distal end 163 of the second extension tube 162 isdisposed within and is secured by the hub 150. A passage 153 within thehub 150 between the proximal end 112 of the outer lumen 110 and thefirst extension tube 160 bends within the hub 150 at an angle ofapproximately 20 degrees away from the longitudinal axis “A”, while theproximal end 122 of the inner lumen 120 and the second extension tube162 both extend along the longitudinal axis “A”. A suture wing 152 isdisposed on the hub 150 to secure the hub 150 to the patient afterinsertion of the catheter assembly 100 into the patient.

Referring back to FIG. 1, a proximal end 164 of the first extension tube160 terminates in a first luer lock 166, while a proximal end 168 of thesecond extension tube 162 terminates in a second luer lock 170. A firsttube clamp 172 is disposed over the first extension tube 160 between thehub 150 and the first luer lock 166, while a second tube clamp 174 isdisposed over the second extension tube 162 between the hub 150 and thesecond luer lock 168.

To manufacture the catheter assembly 100, the inner lumen 120 and theouter lumen 110 are manufactured separately according to known methods,such as by extrusion. After manufacture, the inner lumen 120 is disposedover a first distal mandrel 500 as seen in FIG. 4. The first distalmandrel 500 is an elongated, preferably solid circular cylinder with anouter diameter slightly less than the inner diameter of the inner lumen120 so that the inner lumen 120 is easily slid over the first distalmandrel 500.

A second distal mandrel 510 is partially disposed over the inner lumen120 such that the distal end 124 of the inner lumen 120 extends distallybeyond the second distal mandrel 510. The second distal mandrel 510 isan elongated, open ended hollow cylinder with an inner diameter slightlylarger than the outer diameter of the inner lumen 120, and an outerdiameter slightly less than the inner diameter of the outer lumen 110.

The outer lumen 110 is disposed over the second distal mandrel 510 suchthat the distal end 114 of the outer lumen 110 extends slightly distallyof the second distal mandrel 510, but not as far distally as the distalend 124 of the inner lumen 120. Also, though not shown in FIG. 4, theproximal end 122 of the inner lumen 120 extends exterior of the proximalend 112 of the outer lumen 110. The spacer 140 is disposed over thedistal end 124 of the inner lumen 120, and translated longitudinallyalong the inner lumen 120 until the spacer 140 engages the second distalmandrel 510. The distal ends 124, 114 of the inner lumen 120 and theouter lumen 110, as well as the spacer 140, are treated, such as byultrasonic welding, to fuse the distal end 114 of the outer lumen 110 tothe proximal and exterior portion of the spacer 140 and to fuse theinner portion of the spacer 140 to the inner lumen 120. The spacer 140is also tapered during the fusing to a generally conical shape,providing a smooth transition between the outer diameter of the innerlumen 120 and the distal end 114 of the outer lumen 110. The distal tip130 is also heat treated and shaped to form a tapered shape, as shown inFIG. 2.

After the distal end 104 of the catheter assembly 100 is formed, thedistal mandrels 500, 510 are removed, with the second distal mandrel 510being removed from the proximal end 112 of the outer lumen 110. Thedistal tip 130 and the side openings 118, 128 are manufactured accordingto well-known methods. Next, as shown in FIG. 5, a first proximalmandrel 520 is inserted into the proximal end 122 of the inner lumen120. The first proximal mandrel 520 is an elongated, preferably solidcircular cylinder with an outer diameter slightly less than the innerdiameter of the inner lumen 120 so that the inner lumen 120 is easilyslid over the first proximal mandrel 520. A second proximal mandrel 530is then slid into the proximal end 112 of the outer lumen 110, butexterior to the inner lumen 110. The second proximal mandrel 530 is anelongated, preferably solid piece with a bend 531 of approximately 20degrees, with a distal portion 532 of the second proximal mandrel 530extending approximately 3 cm distal of the bend 531. The distal portion532 tapers from a generally cylindrical cross section to a generallyU-shaped cross-section from the bend 531 to the distal end of the secondproximal mandrel 530. The distal portion 532 forces the proximal end 122of the inner lumen 120 away from the inner wall of the proximal end 112of the outer lumen 110.

The first extension tube 160 is inserted over the proximal end 534 ofthe second proximal mandrel 530 and the second extension tube 162 isinserted over the proximal end 524 of the first proximal mandrel 520.The first and second proximal mandrels 520, 530 are inserted into a hubmold (not shown) with the distal end 161, 163 of each of the first andsecond extension tubes 160, 162, respectively, as well as the proximalend 112, 122 of each of the outer and inner lumens 110, 120, insertedinto the hub mold. A polymer, such as PELLETHANE®, is injected into thehub mold according to well known injection molding methods, forming thehub 150 around the proximal ends 112, 122 of each of the outer and innerlumens 110, 120, the distal ends 522, 532 of the first and secondproximal mandrels 520, 530, and the distal ends 161, 163 of the firstand second extension tubes 160, 162. The hub mold is removed from aroundthe hub 150 and the first and second proximal mandrels 520, 530 areremoved from the proximal ends 161, 163 of each of the first and secondextension tubes 160, 162. The proximal ends 161, 163 of each of thefirst and second extension tubes 160, 162 are each attached to theirrespective luers 166, 170 as is well known in the art.

Alternatively, to manufacture the hub configuration with the spacer 151as shown in FIG. 3A, the spacer 151 is inserted into the proximal end112 of the outer lumen 110 between the outer wall of the inner lumen 120and the inner wall of the outer lumen 110. The second proximal mandrel530 is inserted into the outer lumen 110 between the outer wall of theinner lumen 120 and the inner wall of the outer lumen 110, with theinner lumen 120 disposed between the second proximal mandrel 530 and thespacer 151, to force the inner lumen 120 against the spacer 151. Thefirst proximal mandrel 520 is inserted into the proximal end 122 of theinner lumen 120 to maintain the interior shape of the inner lumen 120.

To manufacture the hub 250 shown in FIG. 3B, referring to FIG. 5A, afirst proximal mandrel 570 is inserted into the proximal end 122 of theinner lumen 120 to maintain the interior shape of the inner lumen 120. Aspacer mandrel 580 having a generally annular cross section is disposedover the exterior of the distal end 122 of the inner lumen 110 and intothe annular space between the outer lumen 110 and the inner lumen 120. Adistal end of the spacer mandrel 580 tapers to a narrower diameter tofit inside the outer lumen 110 and to taper the passageway within thehub 250. The spacer mandrel 580 also includes a keyed portion thatcorresponds with the key 251 b in the spacer 251 as shown in FIG. 3C.The proximal ends 112, 122 of the outer and inner lumens 110, 120, alongwith the mandrels 570, 580 are inserted into a first hub mold 595. Asecond proximal mandrel 590 is inserted into the first hub mold 595 toform the venous passageway 252. The first extension tube 160 is insertedover the second proximal mandrel 590 so that the distal end 161 of thefirst extension tube 160 is within the hub mold 595. Material to formthe hub 250 is then injected into the first hub mold 595.

After the hub 250 cures, the spacer mandrel 580 is removed from thefirst hub mold 595 and the hub 250 is removed from the first hub mold595. The spacer 251 is then inserted into the hub 250 over the proximalend 122 of the inner lumen 120 so that the key 251 b is inserted intothe space formed by the keyed portion of the spacer mandrel 580. Thespacer 251 is inserted until the stepped portion 251 c engages the hub250. Optionally, an adhesive may be applied to the exterior of thespacer 251 prior to inserting the spacer 251 into the hub 250. Thespacer 251 is secured to the proximal end 122 of the inner lumen 120 byapplying a wicking adhesive into each through opening 255.

The hub 250 is then inserted into a second hub mold (not shown) toovermold the hub cap 256. The second extension tube 162 is slid over thefirst proximal mandrel 570 until the second extension tube 162 engagesthe stepped member 254. Material for the hub cap 256 is injected intothe second mold to overmold the hub cap 256 of the proximal end of thehub 250, the spacer 251, and the distal end 163 of the second extensiontube 162.

A second embodiment of a catheter assembly 200 according to the presentinvention is shown in FIGS. 6, 6A, and 7. The catheter assembly 200includes a proximal end 202 and a distal end 204. A longitudinal axis206 extends through the catheter assembly 200 between the proximal end202 and the distal end 204. The catheter assembly 200 is preferablyconstructed from CARBOTHANE® having a hardness of approximately 85 A onthe Shore Durometer scale, or one of the materials disclosed above withrespect to the catheter assembly 100.

The design of the catheter assembly 200 is similar to the catheterassembly 100 described above, with the exception that the distal end 204of the catheter assembly 200 differs from the distal end 104 of thecatheter assembly 100. The proximal end 202 of the catheter assembly 200is preferably the same as the proximal end 102 of the catheter assembly100 as described above, so the proximal end 202 of the catheter assembly200 will not be described. The alternative embodiments of the hubs 150,250 described above and shown in FIGS. 3A and 3B may alternatively beused as well.

The catheter assembly 200 includes an outer lumen 210 having a distalend 212, a proximal end 214, and a body 216 extending therebetween.Preferably, the body 216 has an outer diameter of approximately 0.50 cm(0.20″) and an inner diameter of approximately 0.42 cm (0.16″). Thedistal end 212 is preferably devoid of any side openings and has aplurality of end openings 218 at a distal tip 217 of the outer lumen210. Each of the plurality of end openings 218 is separated from anadjacent end opening 218 by a rib 221. Preferably, three ribs 221 arepresent, although those skilled in the art will recognize that more orless than three ribs 221 may be used.

An inner lumen 220 is disposed within the outer lumen 210 to form apassageway 219 (FIG. 7) having an annular cross section between theinner lumen 220 and the outer lumen 210. The inner lumen 220 includes adistal end 222, a proximal end 224, and a body 226 extendingtherebetween. The body 226 has an outer diameter of approximately 0.30cm (0.12″) and an inner diameter of approximately 0.25 cm (0.10″). Theinner lumen 220 has a plurality of side openings 228 helically spacedalong the body 226 proximate to the distal end 222 of the inner lumen220. Preferably, approximately five side openings 228 are present,although more or less than five side openings 228 may be used.Preferably, also, each side opening 228 has a diameter of approximately0.13 cm (0.05″). A second passageway 229 is formed in the inner lumen220, and serves to return the fluid that was drawn from the patient'sbody by the first passageway 219 and/or add additional fluids, such asmedicaments, into the patient. The second passageway 229 terminatesdistally in a distal tip opening 230.

The ribs 221 space the inner lumen 220 away from the outer lumen 210such that the inner lumen 220 is generally concentrically disposedwithin the outer lumen 210 at the distal end 204 of the catheterassembly 200. Each rib 221 is tapered from a greater to a lesser greaterthickness from the proximal to the distal directions, as well as from agreater to a lesser height from the proximal to the distal directions.

To manufacture the catheter assembly 200, the inner lumen 220 isdisposed over a first mandrel 600 as seen in FIG. 8. The first mandrel600 is an elongated, preferably solid circular cylinder with an outerdiameter slightly less than the inner diameter of the inner lumen 220 sothat the inner lumen 220 is easily slid over the first distal mandrel600. A second mandrel 610 is partially disposed over the inner lumen 220such that the distal end 222 of the inner lumen 220 extends distallybeyond the second mandrel 610. The second mandrel 610 includes a distalend 612 that includes a plurality of spaced cutouts 614. A perspectiveview of the second mandrel 610 is shown in FIG. 8A. The cutouts 614 aretapered so that the cutouts 614 span a larger arc at the most distal end614 a than at the more proximal end 614 b. This taper allows the secondmandrel 610 to be removed from the lumens 210, 220 by sliding the secondmandrel 610 proximally with respect to the lumens 210, 220 after formingthe distal end 204 of the catheter assembly 200.

Referring back to FIG. 8, the outer lumen 210 is disposed over thesecond mandrel 610 such that the distal end 212 of the outer lumen 210extends slightly distally of the second mandrel 610, but not as fardistally as the distal end 222 of the inner lumen 220. The lumens 210,220 and the mandrels 600, 610 are slid longitudinally into a taperedthird mandrel 620 as shown by the arrow B in FIG. 8. Heat is applied andthe distal end 212 of the outer lumen 210 deforms and is forced into thespaced cutouts 614 in the second mandrel 610, forming the ribs 221.Preferably, the heat is applied by RF ultrasonic heating, although thoseskilled in the art will recognize that other heating methods may beused.

The proximal end 202 of the catheter assembly 200 is manufactured in thesame manner as the proximal end 102 of the catheter assembly 100 asdescribed above. The proximal end 202 of the catheter assembly 200 maybe manufactured as shown in FIG. 3, without the spacer 151, or as shownin either of FIG. 3A or FIG. 3B, with either of the spacers 151, 251, asdescribed above with respect to the catheter assembly 100.

Optionally, the catheter assembly 200 may further include a bulbousportion 240, as shown in FIG. 9. The bulbous portion 240 is disposed onthe inner lumen 220 between the ribs 221 and the side openings 228. Thebulbous portion 240 extends distally of the ribs 221 to providesufficient fluid flow into the end openings 218, centering the distalend of the inner lumen within the vessel so as not to restrict fluidintake into the outer lumen 210.

The bulbous portion 240 preferably has an outer diameter ofapproximately 0.50 cm (0.20″), or the same diameter as the outerdiameter of the outer lumen 210. The bulbous portion 240 tapers in aproximal to a distal direction from the larger outer diameter ofapproximately 0.50 cm to the portion of the inner lumen 220 that isdistal of the ribs 221.

To manufacture the catheter assembly 200 with the bulbous portion 240,the catheter assembly 200 is manufactured as described above. Referringnow to FIG. 10, an overmold 250 is formed over the distal end 204 of thecatheter assembly 200 to a location between the ribs 221 and the sideopenings 228 where the bulbous portion 240 is desired. To form theovermold 250, a mandrel 251 is inserted into the distal end 204 of thecatheter assembly 200 to support the distal end 204. The distal end 204of the catheter assembly 200 is then inserted into a mold 252, and bulbmaterial is then injected into the mold 252, forming the overmold 250within the mold 252 in the shape of the bulbous portion 240. Theovermold 250 and the distal end 204 are heated to bond the bulbousportion 240 to the distal end 204 of the catheter assembly 200.Optionally, a secondary forming process, such as RF induction heating,may be performed on the bulbous portion 240 to smooth the transitionbetween the bulbous portion 240 and the exterior of the distal end 204.

The catheter assembly 200 with the bulbous portion 240 is preferablyinserted into the patient as follows. The bulbous portion 240 allows forinsertion of the catheter assembly 200 without the need for anintroducer sheath and/or a dilator, which are commonly used to expand anopening in a blood vessel to accommodate insertion of the catheter intothe vessel. However, a stylet 260 is inserted through the inner lumen220 as shown in FIG. 11. The stylet 260 stiffens the catheter assembly200 to facilitate catheter insertion into the patient. The stylet 260includes a proximal portion 262 that includes a swivel lock connector264. The swivel lock connector 264 is configured to threadably connectto male threads of a luer connector 270 on the proximal end 202 of theinner lumen 220. The stylet 260 also includes a distal portion 266 thatincludes an elongated tubular body 268. The tubular body 268 extendsthrough the inner lumen 220 and extends distally from the distal end 222of the inner lumen 220. The stylet 260 also includes an elongatedopening 269 that extends through the tubular body 268, as well as to andthrough the swivel lock connector 264. The opening 269 has a diameterthat is sized to allow a guide wire to extend therethrough duringcatheter insertion, as will be explained in more detail later herein.

Referring to FIG. 11, to insert the catheter assembly 200 into thepatient, the portion of the catheter assembly 200 located just distallyof the hub 250 may be located within a subcutaneous tunnel 58 in thepatient's body 14, using various well-known tunneling techniques. In onetechnique, the distal end 204 of the catheter assembly 200 is pulledthrough the tunnel 58 from the lower end 59 of the tunnel 58, whileforming the tunnel 58 using a trocar or other tunneling tool, leavingthe hub 250 outside of the tunnel 58 and the distal end 204 extendingoutwardly from an upper end 60 of the tunnel 58 near the area to becatheterized 54. One technique for tunneling the catheter assembly 200through a subcutaneous area is disclosed in U.S. patent application Ser.No. 10/889,816, filed Jul. 13, 2004, which is owned by the assignee ofthe present invention and is incorporated by reference herein as thoughfully set forth.

Next, an incision 50, shown in FIG. 12, is made at the insertion site52, either before or after tunneling. The underlying vessel is thenidentified by aspiration with a syringe or other introducer apparatus,such as the RAULERSON ONE-STEP introducer, near or proximate the area tobe catheterized 54. If the catheter assembly 200 is used forhemodialysis and the area to be catheterized 54 is the internal jugularvessel 56, the incision 50 is made in the clavicular triangle region, asshown for example, in FIG. 12. The exact location of the incision 50 canbe varied by the physician. In accordance with the Seldinger technique,a narrow needle is inserted through the incision 50 and into the vessel56, and the vessel 56 is cannulated. A guide wire 60 is then passedthrough the needle, or other introducer into the cannulated vessel, andthe needle is removed. A proximal end 62 of the guide wire 60 extendsexterior of the patient, with a distal end 64 of the guide wireextending into the vessel 56.

Next, the proximal end 62 of the guide wire 60 is inserted into theopening through the distal portion 266 of the stylet 260 and through thestylet 260 until the proximal end 62 of the guide wire 60 exits theproximal portion 262 of the stylet 260. The catheter assembly 200 isadvanced distally along the guide wire 60 until the distal end 222engages the incision 50 made at the insertion site 52. The distal end222 is advanced through the incision 50 and into the vessel 56 that isbeing catheterized by advancing the catheter assembly 200 in a distaldirection while oscillating the bulbous portion 240 in a circularmotion. The oscillating motion stretches the incision 50 as well as thewall of the vessel 56 where the guide wire 60 penetrates the vessel 56.

As the distal end 222 is advanced into the vessel 56, the bulbousportion 240 further stretches the incision 50 and the wall of the vessel56 so that the distal end 222 may be further advanced into the vessel56. As the bulbous portion 240 advances into the vessel 56, the wall ofthe vessel 56 contracts around the inner lumen 220, proximal of thebulbous portion 240, minimizing blood loss from the vessel 56.

The catheter assembly 200 is further advanced into the vessel 56, andthe ribs 221 engage the wall of the vessel 56. Since the vessel 56 hadjust been stretched by the bulbous portion 240, the wall of the vessel56 easily expands to accommodate the increasing size of the ribs 221 asthe ribs 221 are advanced into the vessel 56. The ribs 221 expand thewall of the vessel 56 to accommodate the outer diameter of the outerlumen 210, which is preferably the same size as the outer diameter ofthe bulbous portion 240, which had just stretched the wall of the vessel56.

After the catheter assembly 200 is inserted a desired distance into thepatient, the guide wire 60 is removed from the proximal end 202 of thecatheter assembly 200 and the stylet 260 by pulling the proximal end 62of the guide wire 60 proximally and out of the stylet 260 in thedirection of the arrow “C”. The stylet 260 is then removed from thecatheter assembly 200 by unthreading the swivel lock 264 from the luerconnector 270 and pulling the stylet 260 proximally from the catheterassembly 200, also in the direction of the arrow “C”.

Next, the incision 50 is closed and the proximal end 202 of the catheterassembly 200 is secured to an external surface of the body 14 such as bysuturing the suture wing 252 on the hub 250 to the body 14.Alternatively, the incision 50 may be closed after securement. Theproximal end 202 of the catheter assembly 200 is connected in fluidcommunication to a hemodialysis unit, or other fluid transfer equipment(not shown), according to procedures well known in the art, and dialysismay now begin.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

1-10. (canceled)
 11. A co-axial catheter comprising: a first lumenhaving a first distal end, a first proximal end, and a longitudinal axisextending therethrough; and a second lumen having a second distal end, asecond proximal end, and extending co-axially with the first lumen,wherein the second lumen is at least partially disposed within the firstlumen; wherein the second distal end extends distally of the firstdistal end, wherein the second distal end includes a distal tip and abulbous projection disposed between the distal tip and the first distalend.
 12. The co-axial catheter according to claim 11, further comprisingat least one spacer disposed between the first distal end and the secondlumen.
 13. The co-axial catheter according to claim 11, wherein thefirst lumen has a first outer diameter and the bulbous portion has asecond outer diameter, wherein the first outer diameter is approximatelythe same size as the second outer diameter.
 14. The co-axial catheteraccording to claim 12, wherein the first distal end includes at leastone opening therein.
 15. The co-axial catheter according to claim 11,wherein the bulbous portion tapers from larger to smaller in a proximalto distal direction.
 16. The co-axial catheter according to claim 11,wherein the first lumen includes a generally U-shaped bend between thefirst distal end and the first proximal end.
 17. (canceled)
 18. A methodof inserting a catheter comprising: providing a catheter having: a firstlumen having a first distal end, a first proximal end, and alongitudinal axis extending therethrough; and a second lumen having asecond distal end, a second proximal end, and extending co-axially withthe first lumen, wherein the second lumen is at least partially disposedwithin the first lumen; wherein the second distal end extends distallyof the first distal end, wherein the second distal end includes a distaltip and a bulbous projection disposed between the distal tip and thefirst distal end; inserting the distal tip into a blood vessel; andoscillating the distal tip in a generally circular motion whileadvancing the distal tip into the vessel.
 19. The method according toclaim 18, further comprising advancing the catheter distally into thevessel such that the bulbous projection is inserted into the vessel, andoscillating the bulbous projection in a generally circular motion whileadvancing the bulbous projection into the vessel.
 20. The methodaccording to claim 18, further comprising, prior to inserting the distaltip into the blood vessel, inserting the distal tip over a guide wire.21. The method according to claim 18, further comprising, prior toinserting the distal tip into the vessel, subcutaneously tunneling thecatheter. 22-30. (canceled)